The present disclosure relates to controlling oil temperature in a vehicle and/or generating electricity in a vehicle. In particular, but not exclusively, the disclosure relates to using a thermoelectric device to control oil temperature and generate electricity in a hybrid vehicle.
The known thermoelectric effect is the direct conversion of temperature differences to electric voltage. A thermoelectric device has a “hot side” and a “cold side” and creates a voltage when there is a different temperature on each side. However, a thermoelectric device can also be operated in a reverse mode in which, when a voltage is applied to the device, the device creates a temperature difference.
It is known to use thermoelectric devices in vehicles for the purpose of generating electricity. The cold side is thermally coupled to a heat exchanger and/or a supply of coolant. For instance, in US 2009/0139207 in the name of Reiners, the exhaust heat is applied to the hot side and the cold side is cooled by a cooling jacket which receives coolant that has passed through a heat exchanger.
Known thermoelectric devices in vehicles may be for the purpose of generating electricity and are not used in the reverse mode.
It is also known that the optimum fuel economy/emissions trade-off for an internal combustion engine is achieved when the coolant is colder than the oil temperature. However, during normal operation of the engine, the oil temperature is typically similar to the coolant temperature. To achieve a larger temperature differential between the oil and coolant, a large heat input to the oil is required. For a typical passenger car this would be around several kilowatts.
Roughly a third of the fuel energy is lost as waste heat in the exhaust gas. This is also at a relatively high temperature compared to the optimal oil temperature, especially during engine warm-up.
When starting from cold, an engine's combustion efficiency is reduced because the cold engine block draws heat out of the cylinder in the compression stroke.
For optimal fuel economy improvements and heat available to the engine for cabin heating, over two kilowatts of heat needs to be pumped into the engine oil during the first 400 seconds on the New European Driving Cycle (NEDC) (a test cycle performed on a cold vehicle typically run at 25° C.). Also, hybrid vehicles tend to have significantly slower warm-up rates and do not recover waste energy except on decelerations. It is desirable to provide a vehicle which is more fuel efficient. It is desirable to do this in a low cost manner without detracting from other functions, such as cabin heating, high heat rejection to the radiator and so on.
It is desirable to increase the warm-up rate of a vehicle, in particular for hybrid vehicles. According to a first aspect of the present disclosure there is provided a vehicle engine comprising: an engine oil reservoir; an exhaust gas system adapted to remove exhaust gas from the engine: and a thermoelectric device having a hot side and a cold side, wherein the thermoelectric device is configured such that the hot side is thermally coupled to the exhaust gas from the engine and the cold side is thermally coupled to the engine oil reservoir.
The present disclosure describes systems and methods to increase the speed of engine warm up by heating oil with a thermoelectric device and also to generate electricity using the same thermoelectric device, exploiting a temperature gradient between engine oil and exhaust gases. The disclosure describes a vehicle engine, comprising: an engine oil reservoir; an exhaust gas system; and a thermoelectric device having a hot side and a cold side and connected to a battery, wherein, the thermoelectric device is configured such that the hot side is thermally coupled to the exhaust gas system and the cold side is thermally coupled to the engine oil reservoir. A diverter valve and duct are provided in the exhaust gas system to selectively convey exhaust gases to the thermoelectric device located in or adjacent to the engine oil reservoir.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Further, the inventors herein have recognized the disadvantages noted herein, and do not admit them as known.